Sebastian is alive because Vargas sister, Pamela Rauseo, knew CPR and put her skills to good use when the cute little boy became stricken along the Dolphin Expressway.

Vargas said her sister was elated at the news that she will have another baby – and was also ecstatic when Sebastian was born.

“When we found out [Sebastian] was a boy, her having three boys, she was like so excited that her kids were going to have another cousin and she started designing his room because that’s what she does,” Vargas told “GMA” about Rauseo, an interior designer. “She just wanted every detail to be so perfect and special for him and it was. It is. It’s a beautiful room and I think he’s happy in there.”

“It was very scary. I get emotional just thinking about it,” Vargas told “GMA.”

Sebastian remains in the hospital as doctors examine him and try to understand why he stopped breathing.

First responders called Rauseo a hero for springing into action so quickly.

She was driving along the traffic-clogged highway when the normally loquacious little boy fell silent. She pulled over and immediately started giving Sebastian mouth-to-mouth while compressing his chest. The boy revived, but then fell unconscious a second time, forcing her to repeat the life-saving procedure.

Miami Herald photographer Al Diaz, snapped photos and called them the best news photos he had even taken.

Rauseo also said she was so freaked out by the emergency she could not get it together to call 911.

“I tried calling 911 because he was completely unresponsive, no matter what I did to call his name, to stimulate him,” Rauseo said on “GMA.”

“I was so nervous my fingers couldn’t dial 911.”

Rauseo had learned CPR years back when her and Vargas’ mother was sick.

“I never thought I would need to perform CPR on anyone, much less my nephew,” said Rauseo, 37.